Become a Site Supporter and Never see Ads again!

Author Topic: Audioroot femto + Upre  (Read 23620 times)

0 Members and 1 Guest are viewing this topic.

Offline pohaku

  • Site Supporter
  • Trade Count: (28)
  • Taperssection Member
  • *
  • Posts: 705
  • Gender: Male
Re: Audioroot femto + Upre
« Reply #15 on: February 24, 2013, 06:35:21 PM »
Which is, of course, why everyone and his brother has jumped into the 500 format business.  Used to be there was just API and Aphex, and that was it.  John Hardy was modular, but not 500 form.  Now, I've lost count of the number of different manufacturers and models out there, with no end in sight.  I've got five of them, bought pretty early on, but haven't seen the need to buy more.  In addition, IMHO, the audible difference between many of them is negligible, despite advertising claims.  That said, if you have AC power access and the space, it is nice to have a full lunchbox of good pres to use for your front end if you are rolling open.  I do find the Femto, Church Audio and Little Box/Tiny Box gear very attractive because they are small and self contained.  Even less to schlep around and cart to a gig.  While there may be different design priorities at work with them, there seems to be no material down side if you take those into account when matching gear to the venue and artist.  Certainly the "studio" market is a bigger pond that the location recording/tapir market, but it is a lot more crowded too.  I'm glad you and Chris can make this niche market work for you.
Mics: akg c460 (ck61, ck63), c414buls, c568eb; at4049a, 4051a, 4053a, at853; josephson c42; neumann U87, km84i; beyer m130, m160, m500; aea r84; gefell m71, mt711s, m200, m201; sony c38; schoeps cmc6, CMBI (mk4, mk21, mk41, mk4v); sennheiser mkh40, md421, md431, md541
Pres: API, a-designs, pendulum, purple, millennia, gt, littlebox, tinybox, usbpre2, CA 9200, pipsqueak, pueblo pending
Cables: KCY, CMR, Naiant AKG actives, PFAs, asst.  GAKables and Darktrain
Recorders/converters: dr680, m10, dr-2d, d50, dr70d, zoom f8, lynx aurora 8


Yeah, I'm an attorney, but everyone needs a day job!

Offline ~Jon Stoppable

  • Trade Count: (46)
  • Needs to get out more...
  • *****
  • Posts: 3328
  • Gender: Male
    • Naiant Studio
Re: Audioroot femto + Upre
« Reply #16 on: February 24, 2013, 07:35:44 PM »
It's because the studio market is not driven by any kind of optimization.  If it were truly a business then there would be cost optimization, especially given the total collapse in rates.  But for the overwhelming majority of studio owners it's really a hobby partially offset by a marginal revenue stream.  So the only limit is the amount of day-job income they are willing to divert to their studios.

Taping is purely a hobby, but it's driven by size optimization.  I don't think I could design without any constraint; I just wouldn't see the purpose.

Offline pohaku

  • Site Supporter
  • Trade Count: (28)
  • Taperssection Member
  • *
  • Posts: 705
  • Gender: Male
Re: Audioroot femto + Upre
« Reply #17 on: February 24, 2013, 09:54:26 PM »
Hah!  True that.  Especially these days.  The number of truly commercial studios has shrunk significantly.  As a hobbyist who has spent stupid money on gear, just because I can, it is interesting to watch the current recording market dynamics.  Outside of a drum room, most local musicians I know either record at home or at a home studio operated by another musician.  I loan out a lot of my gear to friends for their recording projects, simply because I have a much better day job and can afford gear to which they wouldn't otherwise have access.  I don't charge for it, it's my small contribution to the local music scene since I have more gear than talent myself.  So, as you so perceptively note,  cost isn't really a driving factor for me or them in choosing gear.  I certainly don't look at it from an ROI perspective.
Mics: akg c460 (ck61, ck63), c414buls, c568eb; at4049a, 4051a, 4053a, at853; josephson c42; neumann U87, km84i; beyer m130, m160, m500; aea r84; gefell m71, mt711s, m200, m201; sony c38; schoeps cmc6, CMBI (mk4, mk21, mk41, mk4v); sennheiser mkh40, md421, md431, md541
Pres: API, a-designs, pendulum, purple, millennia, gt, littlebox, tinybox, usbpre2, CA 9200, pipsqueak, pueblo pending
Cables: KCY, CMR, Naiant AKG actives, PFAs, asst.  GAKables and Darktrain
Recorders/converters: dr680, m10, dr-2d, d50, dr70d, zoom f8, lynx aurora 8


Yeah, I'm an attorney, but everyone needs a day job!

Offline HazyShadeofWinter

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 15
Re: Audioroot femto + Upre
« Reply #18 on: March 02, 2013, 01:45:28 AM »
It's more midbox sized though.  I kinda think the title is funny, because my naming convention would put midbox at milli, littlebox at micro, and tinybox at pico.  Femto ought to be smaller :D  It's very attractive though and the OLED screen is beautiful.

Keep in mind that I had a very different design philosophy.  Most portable pres are an attempt to run a studio-grade preamp off of batteries, so they have lots of gain (70dB for the Femto) and very low input noise (-129dBu).  Those specs always come at a cost; either input transformers ($, space, and weight) or power.  So Femto idles at 31mA, presumably at 18V (batteries in series, so they aren't hotswappable?), that's 558mW, vs. about 90mW for a tinybox.  The Femto is also spec'ed at 67mA (1.2W) with a pair of CMCs, those draw 4mA each, for 384mW.  So that's about 65% efficient on their phantom conversion circuit; tinybox actually exceeds that a bit, around 70%.

Thus, they end up with a six hour stated runtime for 2x 9V (11.3Wh--it should be longer at nine hours given 1.2W) with the CMCs.  tinybox would manage over eight hours with the same load--but tinybox also has a low-volt phantom option which can run CMCs for over twice as long.

So why spend the power?  Again, for high gain bandwidth and low noise.  That is of benefit if you are using quiet mics on quiet sources.  That's why I have a low-noise amp option on tinybox, which doesn't quite hit the Femto's noise spec; -129dBu is impressively quiet.

I feel embarrassed to ask this question given that you seem to be the person who makes and sells the tinybox, but would you say that for the lowest possible noise at high gain, the Femto seems like the better option?

I understand that one sacrifices size, battery life and initial cost, but from a purely sound engineering perspective, would you say the Femto excels?

Offline ~Jon Stoppable

  • Trade Count: (46)
  • Needs to get out more...
  • *****
  • Posts: 3328
  • Gender: Male
    • Naiant Studio
Re: Audioroot femto + Upre
« Reply #19 on: March 02, 2013, 10:47:42 AM »
I feel embarrassed to ask this question given that you seem to be the person who makes and sells the tinybox, but would you say that for the lowest possible noise at high gain, the Femto seems like the better option?

I understand that one sacrifices size, battery life and initial cost, but from a purely sound engineering perspective, would you say the Femto excels?

Those are really two different questions, the second I can't answer because I don't know the definition of "sound engineering".  Both units are designed for a particular use.  I would highly encourage any taper ordering the Femto to get the lower minimum gain version, because 18dB minimum gain will be too much for many taping situations, and I don't think 70dB is ever necessary (I could write an entire long post on the practical need for high gain; suffice to say that the Femto at max gain has a noise floor of -60dBV, consider if that is useful given an ADC with a likely noise floor of -90dBV or lower).  Does that change maximum gain?  Maybe, probably, they don't say.  If it drops the same 12dB, that makes maximum gain 58dB, not materially different than tinybox's maximum 56dB (I could build a tinybox with more gain, but I don't think that is a useful function).  What does that mean for "sound engineering"?  I have no idea, because that term has no specific meaning.  Both boxes have individual specs that are better than the other, so it comes down to suitability for a particular use.

If your main requirement is lowest possible noise, that is easy:  tinybox low-noise amp is -128dBV A-weighted, Femto is -129dBu (-131dBV), they don't state the weighting (or unweighting).  I'm going to guess that is a weighted figure though, because if unweighted it would be just about the quietest amp on the market, battery-powered or otherwise (the AEA TRP is -130dBu weighted, for example).  So Femto could be 3dB quieter than tinybox.  Whether or not you experience that noise improvement depends on your microphones and your source.  If you are recording very quiet sources with low sensitivity microphones (ribbons, moving-coil dynamics), you might select the Femto.

Offline HazyShadeofWinter

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 15
Re: Audioroot femto + Upre
« Reply #20 on: March 05, 2013, 05:34:05 AM »
Jon,

Thank you for the thorough explanation.

Adam

Offline F.O.Bean

  • Is a 4 channel slut and
  • Trade Count: (116)
  • Needs to get out more...
  • *****
  • Posts: 40356
  • Gender: Male
  • Taperus Maximus
Re: Audioroot femto + Upre
« Reply #21 on: April 16, 2013, 04:37:08 PM »
Cool thread. I'm dying to hear a LB/TB vs. femto comp :)
Schoeps MK4's & MK41's ->
Schoeps & NBob 250/05 KCY's ->
Schoeps VMS02IB & Naiant +60v PFA's ->
DarkTrain Right Angle Stubby XLR's ->
Tascam DR-70D's ->
128gb/64gb SanDisk Extreme Pro SD Cards

http://www.archive.org/bookmarks/diskobean | http://www.archive.org/bookmarks/Bean420 | http://bt.etree.org/mytorrents.php

Offline TSNéa

  • Trade Count: (6)
  • Taperssection Regular
  • **
  • Posts: 137
Re: Audioroot femto + Upre
« Reply #22 on: April 17, 2013, 01:12:11 AM »
If you are recording very quiet sources with low sensitivity microphones (ribbons, moving-coil dynamics), you might select the Femto.
+1. I think Jon explains perfectly how useful / useless a high gain is, depending on your microphones.

I am not an expert with dBv, dBV, dBu, etc. but I can read the specs of a microphone and understand that a sensitivity of 1.5 to 2.5 mV / Pa is very low vs a sensitivity of 10-15 mV / Pa... The first ones are those of a ribbon resp. dynamic microphone, the last ones are common for a condenser one... (I do not consider bandwidth, max level and distortion which can be really important though).
If I use correctly my "Unit Convertor", the difference between 1.5 and 15 mv / Pa is 20 dB in the output level of the mic in the same conditions...

I own an old Beyerdynamic M160, a ribbon microphone that was made to be on top of a boom to record live dialogs in the movies industry, feeding the preamps of a Nagra III or IV: you really want 60 to 70 dB in some circumstances, without noise!

You can download Unit Convertor from here : http://www.sonelec-musique.com/logiciels_freewares_unitconvertor.html
Sorry: it's in French but the numbers are maths!  ;)
« Last Edit: April 17, 2013, 01:14:50 AM by TSNéa »

Offline ~Jon Stoppable

  • Trade Count: (46)
  • Needs to get out more...
  • *****
  • Posts: 3328
  • Gender: Male
    • Naiant Studio
Re: Audioroot femto + Upre
« Reply #23 on: April 17, 2013, 08:26:16 AM »
It puzzles me why sensitivity is ever specified in volts when every other specification is in dB (usually dBV, often A-weighted).  Using decibels converts multiplication and division operations into addition and subtraction, so it's easier for the consumer to understand.

Anyway:

dBV = 20 * log (V)

So, for 1.5mV/Pa and 15mV/Pa:

20 * log ( 0.0015 ) = -56.5dBV/Pa

20 * log ( 0.015 ) = -36.5dBV/Pa

Every decibel measurement is actually a ratio:  dBV is referenced simply to 1V, so it's easy to understand (so the calculations above were actually 20 * log ( 0.015 / 1 ), for example).  The reference level is stated in the suffix:  "V", "u", etc.

dBu should be archaic, but it's still popular with preamp manufacturers.  No one knows why (well they do know, but refuse to admit it's silly).  So while all microphone specifications are in dBV, you have to convert one way or the other to reference to amplifiers.  That is confusing and unhelpful, so I make all of my specifications in dBV.

Anyway, dBu is referenced to the voltage required to drive a 600 ohm load to 1mW.  No one actually cares about power in a preamp circuit, and most preamps are no longer 600 ohm loads.  The "u" means "unterminated", so it's just a reference to a voltage rather than an actual amount of power.  The voltage works out to:

(.001 * 600) ^ 0.5 = 0.775V

So to calculate sensitivity in dBu, you'd have to do this:

20 * log ( 0.0015 / 0.775 ) = -54.3dBu/Pa

But since that is annoying, we can merely observe:

20 * log ( 1 / 0.775) = 2.2dB

So you can convert from dBV to dBu by adding 2.2dB, or just 2dB if you are lazy.

Next up is dBm, which is referenced to the voltage required to drive a specified load to 1mW.  This can vary, but for audio it *usually* means 600 ohm, so it's the same as dBu.  But be careful, because for RF signals it will be referenced to something else, usually 50 ohm or 75 ohm.  RF signal transfer must pay attention to proper termination, so dBm actually matters there.  It does not matter for audio signals, at least before the power amp stage (which are strangely not specified in dBm or maybe dBW, but simply in watts), so dBm is even more archaic than dBu.

Whew, that was a lot of math.  Remember, preamp manufacturers are to blame!

Here's another converter site:

http://www.sengpielaudio.com/calculator-db.htm

.
.
.

I can understand that recording dialog with a ribbon mic would require a low-noise preamp, but understand that there is no such thing as recording "without noise".  That's physically impossible.  The best you can hope for is electrical noise that is quieter than ambient acoustic noise.  For starters, a ribbon mic has self-noise, it's just not specified.  The ribbon mic's transformer has thermal noise from its primary winding, which is stepped up (often 1:40 or so) by the transformer.  The goal is to make the resistance of that winding as low as possible, but typically you end up with a self-noise figure of 17dBA or so.  The noise of the mic preamp, which really can't be much better than that, gets added to the mic's self-noise, so figure for an M160 that the best possible self-noise would be about 21dBA, or about the same as a good lav mic, or many shotgun mics (except the condenser shotgun mics do not put the same noise and gain requirement on the preamp).   Of course when you're recording to tape you have far less dynamic range available and you have to max out levels to get that, so yes you might need 70dB gain there.  But for a condenser mic recording a loud source into a digital recorder with >90dB dynamic range, you would never need 70dB--and a minimum gain of 18dB could be problematic.

Offline TSNéa

  • Trade Count: (6)
  • Taperssection Regular
  • **
  • Posts: 137
Re: Audioroot femto + Upre
« Reply #24 on: April 17, 2013, 08:39:07 AM »
Jon,

Th
"without noise" was just a way to be short, I agree with you!  ;)
I knew that ribbon (and dynamic) microphones had a self nois but didn't thought it was so high...

Offline ~Jon Stoppable

  • Trade Count: (46)
  • Needs to get out more...
  • *****
  • Posts: 3328
  • Gender: Male
    • Naiant Studio
Re: Audioroot femto + Upre
« Reply #25 on: April 17, 2013, 09:03:01 AM »
It's not always so high.  Later-generation dynamics moved to neodymium magnets (Shure Betas, EV NDs, etc.) to increase output a few dB.  That's a direct improvement in self-noise as well.  Some of the modern ribbon microphones use neodyms as well.

Offline TSNéa

  • Trade Count: (6)
  • Taperssection Regular
  • **
  • Posts: 137
Re: Audioroot femto + Upre
« Reply #26 on: April 17, 2013, 09:12:03 AM »
Sorry, my last reply was sent without permission while I was still writing!

Jon,

Thank you for your very precise answer, as usual.
"Without noise" was just a way to be short and conceal my ignorance!  ;)

I knew that ribbon (and dynamic) microphones had a self noise but I didn't know it was that high.
Anyway, I would not put my M160 in front of any PA system in a loud concert...

Jon, you're a kind of Lucky Luke of the electronics: you draw your logarithmic scale faster than your shadow...
http://s62.photobucket.com/user/crimson15_photos/media/lucky_luke_3.jpg.html
 ;D

Offline twoodruff

  • Trade Count: (89)
  • Needs to get out more...
  • *****
  • Posts: 4662
  • Gender: Male
Re: Audioroot femto + Upre
« Reply #27 on: October 04, 2013, 12:23:39 PM »
Ok, I ordered a femto, jhfinn and I will be doing some testings.
Mics
Clamps
Cables
Preamp
Recorders

Offline jbell

  • TDS
  • Trade Count: (125)
  • Needs to get out more...
  • *****
  • Posts: 3692
  • Gender: Male
  • Spreadicated
Re: Audioroot femto + Upre
« Reply #28 on: October 04, 2013, 05:16:02 PM »
What site did you order it from??

Ok, I ordered a femto, jhfinn and I will be doing some testings.
Schoeps MK4's, MK41's> KCY 250/5 Ig> Schoeps VMS 5U> Sony PCM-M10

Offline twoodruff

  • Trade Count: (89)
  • Needs to get out more...
  • *****
  • Posts: 4662
  • Gender: Male
Re: Audioroot femto + Upre
« Reply #29 on: October 04, 2013, 07:41:40 PM »
What site did you order it from??

Ok, I ordered a femto, jhfinn and I will be doing some testings.

Direct from audioroot

Audioroot.fr
Mics
Clamps
Cables
Preamp
Recorders

 

RSS | Mobile
Page created in 0.214 seconds with 36 queries.
© 2002-2017 Taperssection.com
Powered by SMF
Website Design by Foxtrot Media, Inc., a Baltimore Website Company